Question

我创建了一个应用程序，其中我使用CATextLayer添加文本。但我想使用UILabel添加文本并执行缩放和旋转。是否可以通过视频使用UILabel添加文本？如果是的话，请帮我解决这个问题。

我使用CATextLayer添加文本的代码就是这里，它正常工作。

 -(void)displayWatermarkInVideo
  {
if (!self.videoAsset) {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Please Load a Video Asset First"
                                                   delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
    return;
}
AVMutableComposition* mixComposition = [AVMutableComposition composition];

AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo  preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *clipVideoTrack = [[self.videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, self.videoAsset.duration)
                               ofTrack:clipVideoTrack
                                atTime:kCMTimeZero error:nil];

[compositionVideoTrack setPreferredTransform:[[[self.videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];


CALayer *aLayer = [CALayer layer];
aLayer.frame = CGRectMake(0, 0, 30, 30); //Needed for proper display. We are using the app icon (57x57). If you use 0,0 you will not see it
aLayer.opacity = 0.75; //Feel free to alter the alpha here
//Create layer with watermark text instead of image
CGSize videoSize = [self.videoAsset naturalSize];
CATextLayer *titleLayer = [CATextLayer layer];
titleLayer.string = @"Text";
titleLayer.font = (__bridge CFTypeRef)(@"Helvetica");
titleLayer.fontSize = videoSize.height/6;
//?? titleLayer.shadowOpacity = 0.5;
titleLayer.alignmentMode = kCAAlignmentCenter;
titleLayer.bounds = CGRectMake(0, 0, videoSize.width/6, videoSize.height/6); //You may need to adjust this for proper display
//Sorts the layer in proper order
titleLayer.frame = CGRectMake(10, 10, videoSize.width/6, videoSize.height/6);
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
videoLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
[parentLayer addSublayer:videoLayer];
[parentLayer addSublayer:aLayer];
[parentLayer addSublayer:titleLayer]; //ONLY IF WE ADDED TEXT
//Create composition
AVMutableVideoComposition* videoComp = [AVMutableVideoComposition videoComposition];
videoComp.renderSize = videoSize;
videoComp.frameDuration = CMTimeMake(1, 30);
videoComp.animationTool = [AVVideoCompositionCoreAnimationTool      videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
//Create instruction to insert layer
AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, [mixComposition duration]);
AVAssetTrack *videoTrack = [[mixComposition tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVMutableVideoCompositionLayerInstruction* layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
videoComp.instructions = [NSArray arrayWithObject: instruction];

NSString *destPath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)objectAtIndex:0]stringByAppendingPathComponent:@"NewwatermarkVideo.mp4"];
NSURL *exportUrl = [NSURL fileURLWithPath:destPath];



if ([[NSFileManager defaultManager] fileExistsAtPath:destPath])
{
    [[NSFileManager defaultManager] removeItemAtPath:destPath error:nil];
}



AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition
                                                                  presetName:AVAssetExportPresetHighestQuality];
exporter.outputURL=exportUrl;
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;
exporter.videoComposition = videoComp;
[exporter exportAsynchronouslyWithCompletionHandler:^{
    dispatch_async(dispatch_get_main_queue(), ^{
        [self exportDidFinish:exporter];
    });
}];
}

Answer 1

您可以使用CALayer和CATextLayer，然后应用转换和缩放。如下所示

CATextLayer *textLayerFront = [CATextLayer layer];
textLayerFront.doubleSided = NO;
textLayerFront.string = @"Front";
textLayerFront.contentsScale = [[UIScreen mainScreen] scale];

CATextLayer *textLayerBack = [CATextLayer layer];
textLayerBack.doubleSided = NO;
// Eventually both sides will have the same text, but for demonstration purposes we will label them differently.
textLayerBack.string = @"Back";
// Rotate the back layer 180 degrees relative to the front layer.
textLayerBack.transform = CATransform3DRotate(textLayerBack.transform, M_PI, 0, 1, 0);
textLayerBack.contentsScale = [[UIScreen mainScreen] scale];

如何通过在视频上使用UILabel而不是CATextLayer来添加文本

1 个答案: